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<p>The intriguing physical phenomena associated with exceptional points have established non-Hermitian physics as a frontier of modern research. Recent investigations have extended non-Hermitian physics into the fully quantum domain. However, existing studies predominantly concentrate on discrete-variable quantum systems, while non-Hermitian quantum effects in continuous-variable encoded systems remain largely unexplored. In this work, we investigate the exceptional structure for a driven-dissipative Kerr-cat qubit, realized with a Kerr nonlinear resonator. We find that the dissipation leads to a bidirectional jump between the two basis states of the cat qubit, which is in distinct contrast with the unidirectional jump associated with normal two-level systems. The competition between this jump and a single-photon drive gives rise to the emergence of third-order Liouvillian exceptional points (LEP3s), each of which corresponds to a crossing point of two lines of LEP2s. Crucially, the single-photon drive is essential for generating the observed nontrivial Liouvillian topology, which reduces to a trivial case when the drive is turned off. We further show that the LEP3 can exhibit the topological character of the Hamiltonian EP3s, which cannot be realized with a single qubit. Our work opens the possibility of realizing non-Hermitian phenomena with continuous-variable quantum systems.</p>

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Non-Hermitian topology in a single driven-dissipative Kerr-cat qubit

  • 期刊论文

  • 发表日期：

    2026年4月28日

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  • Pei-Rong Han,
  • Huiye Qiu,
  • Hao-Long Zhang,
  • Wen Ning,
  • Zhen-Biao Yang,
  • Shi-Biao Zheng

摘要

The intriguing physical phenomena associated with exceptional points have established non-Hermitian physics as a frontier of modern research. Recent investigations have extended non-Hermitian physics into the fully quantum domain. However, existing studies predominantly concentrate on discrete-variable quantum systems, while non-Hermitian quantum effects in continuous-variable encoded systems remain largely unexplored. In this work, we investigate the exceptional structure for a driven-dissipative Kerr-cat qubit, realized with a Kerr nonlinear resonator. We find that the dissipation leads to a bidirectional jump between the two basis states of the cat qubit, which is in distinct contrast with the unidirectional jump associated with normal two-level systems. The competition between this jump and a single-photon drive gives rise to the emergence of third-order Liouvillian exceptional points (LEP3s), each of which corresponds to a crossing point of two lines of LEP2s. Crucially, the single-photon drive is essential for generating the observed nontrivial Liouvillian topology, which reduces to a trivial case when the drive is turned off. We further show that the LEP3 can exhibit the topological character of the Hamiltonian EP3s, which cannot be realized with a single qubit. Our work opens the possibility of realizing non-Hermitian phenomena with continuous-variable quantum systems.